The present invention can be used in an alarm control for an apparatus for dispensing volatile anesthetics, also called vapors, which said apparatus is controlled by means of a handwheel where dispensing, which cannot be guaranteed as a consequence of the lack of operating voltage, must be prevented from being set with the handwheel when the apparatus is switched off or in case of failure of the operating voltage.
Electricity, which is taken from a supply network, is usually necessary for the operation of an anesthetic dispensing apparatus. The dispensing proper is carried out by means of a mechanically adjustable assembly unit with variable flow cross section. The dispensing operation is controlled, monitored and secured by various electronic assembly units during normal operation. Critical states of operation are avoided or displayed by software-assisted warnings or alarm reports. Some of the functions intended for this are dispensable when the apparatus is put out of operation.
However, if the apparatus is not ready to operate, for example, because of the energy supply being interrupted or switched off, the user must be alerted about this at least when there is a risk for no dispensing or dispensing of an insufficient quantity of anesthetics. This function must not depend on the supply of the operating voltage via the supply network or the functioning of the software.
In case of conventional anesthetic dispensers with handwheel, securing against the incorrect dispensing or dispensing of an insufficient quantity of anesthetics is achieved by the handwheel for setting the dispensing concentration being locked in the zero position when the operating voltage from the supply network fails. It is thus impossible to set a dispensing concentration with the energy supply switched off when the handwheel was in the zero position at the time of interruption of the operating voltage.
However, this locking only becomes active in the zero position of the handwheel. However, if the energy supply fails at another concentration setting, an acoustic alarm of a limited duration in time is triggered, but the concentration setting continues to be able to be changed. The locking of the handwheel is subject, moreover, to mechanical wear and may be damaged by forcibly rotating the locking handwheel.